Conditional knock-out of integrin-linked kinase demonstrates an essential role in protein kinase B/Akt activation

J Biol Chem. 2003 Jun 20;278(25):22374-8. doi: 10.1074/jbc.M303083200. Epub 2003 Apr 8.


Protein kinase B (PKB/Akt) plays a pivotal role in signaling pathways downstream of phosphatidylinositol 3-kinase, regulating fundamental processes such as cell survival, cell proliferation, differentiation, and metabolism. PKB/Akt activation is regulated by phosphoinositide phospholipid-mediated plasma membrane anchoring and by phosphorylation on Thr-308 and Ser-473. Whereas the Thr-308 site is phosphorylated by PDK-1, the identity of the Ser-473 kinase has remained unclear and controversial. The integrin-linked kinase (ILK) is a potential regulator of phosphorylation of PKB/Akt on Ser-473. Utilizing double-stranded RNA interference (siRNA) as well as conditional knock-out of ILK using the Cre-Lox system, we now demonstrate that ILK is essential for the regulation of PKB/Akt activity. ILK knock-out had no effect on phosphorylation of PKB/Akt on Thr-308 but resulted in almost complete inhibition of phosphorylation on Ser-473 and significant inhibition of PKB/Akt activity, accompanied by significant stimulation of apoptosis. The inhibition of PKB/Akt Ser-473 phosphorylation was rescued by kinase-active ILK but not by a kinase-deficient mutant of ILK, suggesting a role for the kinase activity of ILK in the stimulation of PKB/Akt phosphorylation. ILK knock-out also resulted in the suppression of phosphorylation of GSK-3beta on Ser-9 and cyclin D1 expression. These data establish ILK as an essential upstream regulator of PKB/Akt activation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Base Sequence
  • Bone Marrow Cells / enzymology
  • Cell Line
  • DNA Primers
  • Enzyme Activation
  • Gene Deletion*
  • Humans
  • Phosphatidylinositol 3-Kinases / metabolism
  • Polymerase Chain Reaction
  • Protein Serine-Threonine Kinases / genetics*
  • Protein Serine-Threonine Kinases / metabolism*
  • Protein-Tyrosine Kinases / metabolism*
  • Proto-Oncogene Proteins / metabolism*
  • Proto-Oncogene Proteins c-akt
  • RNA, Small Interfering / genetics
  • Recombinant Proteins / metabolism
  • Transfection


  • DNA Primers
  • Proto-Oncogene Proteins
  • RNA, Small Interfering
  • Recombinant Proteins
  • integrin-linked kinase
  • Protein-Tyrosine Kinases
  • AKT1 protein, human
  • Protein Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt